Barbatula nuda: an economically valuable freshwater fish that accepts phytoplankton as first food.

Barbatula nuda is considered a promising emerging species to diversify small cold-water fish aquaculture worldwide due to its rapid growth and delicious flesh. However, limited information on larval development and nutrition is available. In this study, 7-day feeding experiments were performed to evaluate three different initial diets (zooplankton, phytoplankton, and artificial microdiet) in the zoo group, algae group, and AD group on growth, development, and digestion of larvae B. nuda. The results showed that there was no significant difference in survival rate among the three groups (p > 0.05). The algae group exhibited the highest feed intake success rate and body weight (p < 0.05), the best intestinal development with the protruded intestinal mucosa, and visible intestinal microvillus. Pepsase and trypsin enzyme activities in the algae group larvae were significantly higher than those in the other two groups (p < 0.05). Transcriptome data showed that the mechanistic target of rapamycin pathway of B. nuda fed with phytoplankton was activated, and the metabolisms of carbohydrate were significantly more active than those in the other two groups. As omnivorous fish, B. nuda could accept zooplankton, phytoplankton, and microdiet as initial diets with its survival unaffected, but B. nuda fed with phytoplankton exhibited better growth status and digestive tract development and higher digestive enzyme activities than those fed with other two diets. Therefore, phytoplankton was a suitable initial diet for B. nuda. Our findings provide guidance for the artificial breeding of B. nuda and a theoretical basis for research on fish initial diet.